The result is a complex interplay between both: the PTSD activating the personality disorder, and the personality disorder fueling the PTSD.

A recent case was a truck driver who was involved in a single vehicle accident, which resulted in severe physical injuries. After assessing the driver, it was clear that he had a pre-morbid antisocial personality disorder.

The truck driver's childhood was one of rejection and violence, shaping him into an impulsive, aggressive man with ongoing intense fear of further rejection. He had turned people away throughout his adult life with a biker image and violent tendencies, and he had become distrustful, suspicious and resentful of almost all people he came across in his life.

When the accident occurred, he experienced classic post-trauma symptoms of re-experiencing, avoidance and hyperarousal. However, he also experienced burning anger. He was angry with his employer, the doctors who operated on him, the police who investigated the accident, and the insurance company that had provided him with cover. He maintained this rage: he said, "If I don't maintain the rage they will screw me, just like people have screwed me all my life."

The bi-directional influence from PTSD to personality disorder and vice versa makes the treatment of this case very complex. In this case, I needed to know where to begin intervention, what the focus should be, and what might be reasonable therapeutic goals.

It was clear that the goal of treatment was not to find a cure for all of this man's problems, but to work towards modifying his thoughts and behaviours.

Key thoughts and behaviours that people with personality disorders need to modify are impulsiveness, compulsiveness, inflexibility, extreme and oppositional way of thinking, and tendency towards interpersonal conflict. Interwoven with this is the trauma specific therapy, which helps the clients to regulate their affect, manage their intrusive thoughts and memories, and return, if physically possible, to pre-trauma levels of functioning.

Even when clients have strong motivation to change, many will lack the basic skills to do so. And, unfortunately, in the climate of brief interventions, it is often very difficult to find adequate time for making the necessary changes. Nevertheless, psychologists return to the fundamentals of therapy for these clients. These include:

• A strong therapeutic relationship stressing the importance of collaboration,
• A thorough assessment of all the client's presenting problems and background,
• An accurate conceptualisation that can explain the client's past behaviours, make sense of the client's present experience, and help plan for the future,
• A useful therapeutic approach, often cognitive behavioural in nature, addressing real change in the client's thoughts and behaviours.